1. Field of the Invention
The present invention relates to an automatic original conveying device and an image forming apparatus.
2. Description of the Related Art
An automatic original conveying device is provided in image forming apparatuses. In the image forming apparatuses, originals, which have been set on an original mounting platen in such a state that the image surface of each original faces upward, are successively separated one by one from the uppermost original, are reversed, are conveyed to a predetermined reading position, and as such are delivered without stopping. Copying machines, facsimile machines, and scanners are the examples of the image forming apparatuses.
Japanese Patent Application Laid-open No. H9-166896 discloses an automatic original conveying device. This automatic original conveying device includes an original mounting platen for mounting originals, a separating/conveying unit that separates and conveys the originals mounted on the original mounting platen successively one by one from the uppermost original, a first conveying path that receives the original from the separating/conveying unit, reverses the original and conveys the reversed original to a reading position provided below the original mounting platen, a paper delivery path that conveys the original from the reading position to an original delivery port, an original delivery table that is provided at a position below the original mounting platen and on an extension of the paper delivery path, a switchback conveying path provided between the original mounting platen and the original delivery table, a switching member that can perform switching between a switching position at which the paper delivery path is communicated with the original delivery port and a switching position at which the switchback path is communicated with the paper delivery path, and a pair of paper delivery rollers that is provided on an upstream side of the switching member in a conveying direction of the original so as to be rotatable in normal and reverse directions. When the original has been led to the switchback conveying path, the paper delivery rollers are rotated in a reverse direction in such a state that the rear end of the original is held between the paper delivery rollers to switchback the original from the switchback conveying path to the second conveying path. In this structure, the original can be switched-back and can be reversed and again returned to the reading position, and, thus, a small-sized automatic original conveying device, which has a shorter original conveying path, for reading both sides of the original can be provided.
Japanese Patent Application Laid-open No. H8-133551 discloses a sheet conveying device for an image reading device. This sheet conveying device includes a sheet pressing unit that presses a sheet mounted on a platen against the surface of the platen, a sheet mounting unit that is provided above the sheet pressing unit and receives sheets in a stacked state, a conveying unit provided with a conveying path that receives the sheet from the sheet mounting unit through an inlet side, allows the sheet to be passed through the reading position, at which the image on the sheet is read, and delivers the sheet through a paper delivery port, and a switchback path that is provided between the sheet pressing unit and the sheet mounting unit and leads the sheet, passed through the reading position, by switchback conveying to the inlet side of the conveying path. The sheet conveying device includes a pair of switchback rollers provided in the switchback path and including a pair of rollers that perform switchback conveying of the sheet passed through the reading position, and a roller spacing unit that spaces rollers constituting the switchback rollers from each other. The switchback rollers serve also as the sheet delivery unit. A registration unit that adjusts timing of sheet alignment and sheet feeding is provided on the downstream side of a point at which the conveying path meets the switchback path. The registration unit includes a pair of rollers that comes into rolling contact with each other. The conveying unit includes a plurality of large-diameter wheel-shaped axially-arranged members. The point of rolling contact in the rollers is provided on a circumference of the wheel-shaped members. The backside of the sheet pressing unit may be configured as a part of the switchback path.
Japanese Patent Application Laid-open No. 2002-77519 discloses a double-sided original reading device. In this original reading device, a conveying unit in a conveying system is rotated in a sheet original conveyance direction by normal rotation of a single driving source. A conveying unit in a delivery system is rotated in a direction in which the sheet original undergoes switchback reversing. A conveying unit in a scanning system including a registration roller is rotated, by reverse rotation of the single driving force, in a direction, in which the sheet original is conveyed to a reading unit and is read, and the conveying unit in the delivery system is rotated in a direction in which the sheet original is delivered. The double-sided original reading device is characterized in that, upon detection of the passage of the sheet original with the resist sensor, the single driving source is switched from normal rotation to reverse rotation.
Japanese Patent Application Laid-open No. 2000-89524 discloses an original conveying device. In this original conveying device, when a motor is rotated in a normal direction, the paper delivery roller is rotated in the normal direction to convey the original in a paper delivery direction. On the other hand, when the motor is rotated in a reverse direction, the paper delivery roller is rotated in the reverse direction to convey the original to a reverse conveying path. Moreover, when the motor is rotated in a normal direction, a PS roller is rotated in a normal direction to send the original to an original reading position, and, when the motor is rotated in a reverse direction, a clutch is released to stop the rotation.
In many original conveying devices requiring switchback reversing described in Japanese Patent Application Laid-open No. H9-166896, two motors, that is, a motor that drives a switchback roller, and a motor that drives another conveying roller, are used to drive the conveying roller in a given direction independently of normal and reverse rotations of the switchback roller. This arrangement however makes the structure complicated.
In the sheet conveying device disclosed in Japanese Patent Application Laid-open No. H8-133551, when a roller spacing unit, which spaces rollers constituting the switchback rollers from each other, is used, an operating unit such as a solenoid is necessary in the roller spacing unit. Also, when the switchback conveying path is used, an operating unit such as a solenoid is necessary as a switching unit for a switching member which is switchable to a switching position at which the switchback path is communicated with the paper delivery path. In this structure, control such as synchronization control becomes complicated leading to problems such as increased cost.
In the original reading device disclosed in Japanese Patent Application Laid-open No. 2002-77519, for example, the driving source is rotated in normal and reverse directions, and a switching member, which can perform switching to a switching position at which a paper delivery path is communicated with an original delivery port and switching to a switching position at which a switch back path is communicated with the paper delivery path, is operated by a driving source provided separately from a driving source that performs switching between normal rotation and reverse rotation of the switchback roller. This arrangement however makes the control complicated.
In the original conveying device disclosed in Japanese Patent Application Laid-open No. 2000-89524, as with the sheet conveying device disclosed in Japanese Patent Application Laid-open No. H8-133551, the original conveying device suffers from problems such as increased cost as a result of complicated control such as synchronization control.